Quail farms become widely spread in Egypt as a source of meat. Early mortality of quailchicks is one of quail breeding limiting factors. This study was performed to study role ofsome Enterobacteriaceae as a parable cause of early mortality in South Valley Universityquail farm, characterize isolates phenotypically and serologically, determine theirantimicrobial sensitivity and to screen all isolates for presence of florfenicol resistance gene(floR), Quaternary ammonium compounds resistance gene (QacA/B) and class 1 integronsgene (Int1) and to screen E. coli, Salmonella and K. pneumoniae isolates for intimin encodinggene (eaeA), invasive encoding gene (invA) and mucoviscosity associated gene (magA)respectively. Therefore, 80 freshly dead or moribund Japanese quail chicks under 12 days ofage were collected from this farm during the period from December 2020 to April 2021 forclinical assessment and bacterial isolation. Totally, 14 E. coli, 6 Salmonella and 1 K.pneumoniae isolates were isolated and phenotypically identified from the internal organs ofthe examined quail chicks with percentage of (17.5%), (7.5%) and (1.25%) respectively. E.coli isolates belonged to 5 different O-serogroups comprising O86 (28.6%), O78 (21.4%), O26(14.3%), O55 (14.3%) and O164 (7.1%) in addition to 2 nontypeable isolates (14.3%) while allSalmonella isolates were serologically identified as S. Typhimurium with antigenic formula1,4,[5],12:i:1,2. All isolates were weak biofilm producer except (33.3%) of S. Typhimuriumisolates and showed Congo red binding activity except (28.6%) of E. coli isolates while only(14.3%) of E. coli isolates had hemolytic activity. Antimicrobial susceptibility testing for theisolates to 10 different antibiotics revealed that all the isolates were sensitive only tochloramphenicol and oxytetracycline except (42.9%) and (85.7%) of E. coli isolatesrespectively and to azithromycin except (35.7%) of E. coli isolates and K. pneumoniae. PCRrevealed that all the isolates harbor Int1 and floR genes, (100%) and (33.3%) of S.Typhimurium isolates harbor invA and QacA/B genes respectively and only (21.4%) of E. coliisolates harbor eaeA and QacA/B genes. It was concluded that E. coli and S. Typhimurium area major cause of early mortality of Japanese quail chicks.